In the past two years we have discovered OMPase, an OMP specific 5'-nucleotidase and a series of uridine phosphorylase inhibitors, namely, pyrimidine acyclonucleosides, 1-(2'-hydroxyethoxymethyl) uracial and its derivatives. Proposed in this application are: (1) Purification and Characterization of OMPase, thymidine phosphorylase and uridine phosphorylase; and (2) Determination of profiles of enzymes of pyrimidine salvage pathways in about 20 different normal and malignant cells. For the purification of uridine phosphorylase, we will attempt to develop affinity chromatography materials be attaching one or more of the most potent pyrimidine acyclonucleosides to Sepharose through an arm such as the aminoethyl group. If successful, these materials will be used to purify uridine phosphorylases from various tissues including human tumors grown as xenografts in nude mice. For the purification of thymidine phosphorylase and OMPase, we will apply more conventional methods. The data from the enzyme profile survey will be analyzed to delineate correlations among the enzymes of pyrimidine salvage enzymes, namely, nucleoside phosphorylases, 5'-nucleotides, pyrimidine nucleoside kinases and orotidine phosphoribosyltransferase. These studies, we hope, will indicate the feasibility of using uridine phosphorylase inhibitors as single cancer chemotherapeutic agents or as modulators of existing pyrimidine drugs such as FU, FUdR and PALA.